Senate Majority Leader Chuck Schumer (D-N.Y.) told Politico that the progressive and moderate wings of the Democratic Party "each need each other" in order to have any hopes of passing their spending priorities with the narrowest possible majority.

Why it matters: Democrats have cleared the first hurdle in Schumer's risky "two-track" legislative strategy to enact President Biden's agenda, but just a single objection could derail the entire gambit.

• The Senate this week overwhelmingly approved the $1.2 trillion bipartisan infrastructure package, despite reluctance from some progressives.
• Hours later, all 50 members of the Senate Democratic caucus passed a $3.5 trillion budget resolution — teeing up a fight over a mammoth spending package that moderates are highly skeptical of.

What they're saying: "The moderates couldn't pass a bipartisan bill without the more progressive wing of our caucus," Schumer told Politico. "And the progressives couldn't get a big, bold bill without the moderates."

Behind the scenes: A few weeks before Tuesday's vote, Schumer says he negotiated with Senate Budget Chairman Bernie Sanders (I-Vt.) — who was once the most vocal "no" on the plan — telling him that "if you want the moderates to vote with the progressive vision, you can't vote no on this. You don't have that luxury."

• Schumer recounts then telling centrist Democrats Joe Manchin (D-W.Va.) and KyrstenSinema (D-Ariz.): "If you won't vote yes on the budget resolution, I can't get them to vote yes" on the bipartisan bill.
• Schumer says his strategy is "not mysterious. I preach how we each need each other. And without unity we have nothing." But the hardest part is still to come.
• Almost immediately after the Senate cleared a budget that sets up a $3.5 trillion spending bill, Manchin said he has "serious concerns" about the size of the budget package, calling it "simply irresponsible" to continue spending at such high levels.
• Schumer acknowledged there will be "a lot of hashing it out and clashing around in the reconciliation." But he promised that no matter the compromise, the Senate will pass "every part of the Biden plan in a big, bold, robust way."

What to watch: Schumer said at a press conference Wednesday that Senate committee chairs will work intensely over the next few weeks with the goal of having a reconciliation bill — presumably one that satisfies the concerns of both moderates and progressives — completed by Sept. 15.